Microglia play a critical role as immune cells in the central nervous system (CNS), helping protect the nervous system in response to neural damage or inflammation. Microglia are also thought to play a role in neurodegenerative disorders such as Alzheimer's disease, dementia, multiple sclerosis and amyotrophic lateral sclerosis (ALS). Microgliosis – the accumulation of microglia – is a common response to multiple types of damage within the CNS. However, the origin of microglia involved in this phenomenon remains elusive. It has been shown that, as a result of radiation therapy or bone marrow transplant, this increase may be due to recruitment of bone marrow-derived progenitor cells that are capable of forming microglia. In the absence of therapies that manipulate the body’s blood production system, however, this is not the case. Bahareh Ajami has observed in her previous studies that recruitment does not account for the massive increase in microglial cells that occur in two different CNS disease models: neurodegeneration and traumatic injury. Instead, microgliosis is solely the result of the expansion (division and growth) of microglia already residing in the CNS. She is now working to determine whether bone marrow-derived progenitor cells have a role in microglia accumulation in multiple sclerosis, which is an autoimmune disease of CNS. In parallel, she will also explore the effect of microglial cells on nerve cell survival in the CNS. Ajami’s results will not only contribute to the field of neuroscience, but could also provide new targets for developing gene and drug delivery systems that treat CNS disease.